1. Field of the Invention
The present invention pertains generally to methods for sizing masks, and, more particularly, to a method for sizing a mask used to treat a patient who suffers from disordered breathing. The present invention also relates to devices used in sizing such masks and methods for providing such masks.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube into the patient's esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver positive airway pressure (PAP) therapy to treat certain medical disorders, the most notable of which is OSA. Known PAP therapies include continuous positive airway pressure (CPAP), wherein a constant positive pressure is provided to the airway of the patient in order to splint the patient's airway open, and variable airway pressure, wherein the pressure provided to the airway of the patient is varied with the patient's respiratory cycle. Such therapies are typically provided to the patient at night while the patient is sleeping.
Non-invasive ventilation and pressure support therapies as just described involve the placement of a patient interface device including a mask component having a soft, flexible sealing cushion on the face of the patient. The mask component may be, without limitation, a nasal/oral mask that covers the patient's nose and mouth, a nasal mask that covers the patient's nose, a nasal cushion that rests beneath the patient's nose (such as a “pillows” style nasal cushion having nasal prongs that are received within the patient's nares or a “cradle” style nasal cushion that rests beneath and covers the patient's nares), or a full face mask that covers the patient's face.
Traditionally masks used for respiratory therapy are generally sized such that the length, width, and/or depth of one size of a given mask accommodates a prescribed subpopulation of users, and a set of such sizes (which vary in length, width, and/or depth) are developed such that the corresponding facial geometry of almost any user among the entire population of users is accommodated by at least one size of mask from the set.
As an example, sizing for a nasal mask, such as the example mask 10 shown in FIG. 1, has traditionally been accomplished by increasing the length L and (in some cases) the width W as the sizes progress from the smallest to the largest, such as shown by the sizing gauge 12 of FIG. 2, while the depth D (FIG. 6) is held constant such that the nasal protrusion of any user is accommodated by every size in the set.
As another example, sizing for a cradle mask, such as the example mask 20 shown in FIG. 3, has traditionally been accomplished by increasing the width W and/or depth D of a cushion 22 as the sizes increase from the smallest to the largest. FIG. 4 shows example top views of small S, medium M and large L versions of cushion 22. Variations in length (i.e., the dimension into the page of FIG. 4) are not typically applicable to this style of cushion since it sits under the nose of a patient and does not engage with the nasal bone.